


Death Note

by ThatSeance



Category: Supernatural
Genre: Alternate Universe, Alternate Universe - Detectives, Angst, Angst and Hurt/Comfort, Castiel as L, Death Note AU, Death Note Musical, Handcuffed Together, Hurt Sam Winchester, Justice, M/M, Morally Grey Sam Winchester, POV Sam Winchester, POV Third Person, Police Brutality, Sharing a Bed, Time Skips, if you cant find the fic write it yourself huh, sam winchester as Light, you do not need to know death note to read this
Language: English
Status: Completed
Published: 2020-07-29
Updated: 2020-07-29
Packaged: 2021-03-06 02:21:40
Rating: Teen And Up Audiences
Warnings: Major Character Death
Chapters: 1
Words: 4,151
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/25595701
Author URL: https://archiveofourown.org/users/ThatSeance/pseuds/ThatSeance
Summary: Sam Winchester has always had an acute sense of right or wrong. He feels like there's a lack of justice in the world, and when the reaper Ruby gives him an opportunity to create balance, there's no question what to do: kill all evildoers. However, there's a certain black haired detective distracting him from his goal....Supernatural Death Note AU.
Relationships: Castiel/Sam Winchester, implied
Comments: 2
Kudos: 11





	Death Note

**Author's Note:**

> My 2 am brain thought this was genius and now there's 4k words on it so. Here we are!
> 
> This is only vaguely accurate to canon death note plotlines. It's mostly based off of the musical and the vague bits I remember from 2015. Which, by the way, all of the songs between Light and L in the musical are absolutely the soundtrack to this fic. 
> 
> With that said, I hope you enjoy! Kudos and Comments are greatly, greatly appreciated <3

"So this notebook.... it really kills people with just a name and a face. You write it in and they're dead."

The woman smirks. "Now you're getting it."

"Then.... I could revolutionize the system. I could execute those who do wrong." The boy grins back. "I could finally bring justice to the world."

"But Sam, you have to be careful," The woman remarks, biting into a glistening red apple, "You can't let anyone know you have that journal."

Sam scoffs. "I'm not an idiot, Ruby. I know what I have to do. Don't you see? This is the way I can fix the world. I have to do this."

Ruby's eyes sparkle. "Whatever you say, Sam."

* * *

"Dean? Where'd you get a name like that, anyways?" Ruby asks, laying across Sam's bed. She tosses an apple between her hands, looking as if she were bored to death.

The sound of pencil on paper slowly halts. Sam stares down at the notebook in front of him (the tool to salvation) and clenches the wood between his fingers. He exhales harshly and pushes himself away from the desk to turn his chair towards Ruby. "Why do you wanna know?"

Ruby shrugs. "I'm curious. I mean, seems kind of out of nowhere. Of all the names, why would you call your killing persona Dean?"

Sam leans back in his chair. He stares at the wall behind Ruby for a moment, seeming to consider something, before speaking, "It's the name of my dead older brother, Dean."

Ruby pushes herself up on the bed. "Oh?" 

"It was officially labeled as an accident." Sam rolls his eyes. "Killed on the job. He was a detective, like my dad, y'know? But things didn't add up. I mean, what accident leads to multiple bullet wounds in the chest? He was murdered. And no one was ever arrested for it." Sam turns back towards the desk. "That's why I used his name publicly. I want him to be.... immortalized, you could say."

"I see." Ruby lays back down on the bed. "That's rough, kid."

Sam scoffs. "Yeah. It is."

* * *

"Why'd they even bring this guy in?"

"Well, no one's made any progress with the Dean case. Supposedly, he's the top detective in the country. Frankly, he doesn't seem like much to me."

"I mean, are we just supposed to trust a voice on a computer?"

Sam glances over at the men talking in the corner. It had been three months since he'd received the death note from Ruby, and ever since, he's been systematically killing off the criminals of the world one by one. The method of death varies person to person, but he typically went with a heart attack. He's built up a fan base online, who chant for the death of politicians and criminals. It's flattering, in a way, even if they don't know who he is. 

He approaches the men from behind, and puts on his best friendly smile and puppy dog look. "Excuse me, who are you talking about?"

One of the men turns around. "Oh! It's John's son."

The other one follows. "Oh! Hey, Sam, how've you been?"

"Good, I'm doing good." He looks at them earnestly. "Who were you two talking about?"

"Oh, well..." One of the men scratches behind his ear. "We aren't strictly allowed to tell you this, but.... It's this private detective they brought in for the Dean case. He goes only by 'Cas'. No one knows what the hell he stands for. He basically just calls in for every meeting."

The other one interjects. "Everyone's wondering if he even really cares about the people who are dying."

Sam frowns. "That doesn't seem like a very just detective."

The second man gestures towards Sam. "Exactly!"

The first man chuckles a little, before turning towards Sam, giving him a wink. "Don't tell anyone we told you, alright kid?"

"You got it." Sam smiles brightly. "I mean, what would I do with the info anyways?"

* * *

"Cas, huh?" Ruby flips through the channels on the tv. "Doesn't seem that intimidating. What's he got against you?"

"Nothing yet. But he's a private detective, the top one in the country, which means I need to be more careful. I need to think a step ahead of him." 

"Seems like a lot of effort." Ruby stops flipping through channels and lands on a man's face. "What's this?"

From the screen, a man drawls out, "....I am the new detective on the Dean case, Casper Novelle. I swear to follow this case through until the end...."

Sam's eyes are glued to the screen. He laughs in shock. "Is he an idiot? He just gave me his name and face. He's done for."

"Well, it's not like everyone knows you just need a name and face." Ruby glances over at Sam, who's frantically writing in the notebook. "Won't it be weird if he dies on live TV?"

Sam shakes his head. "It'll just show them not to mess with Dean." He turns his head back to the screen as he lifts the pen off of the paper.

The man on the screen continues to talk for a few seconds, before pausing. He begins to cough, deep from within his chest, until blood splatters onto the table and he collapses against the wood with a deafening 'thud'. Sam grins, wide and proud, cheering in his head.

That is, until a voice echoes out of the tv. "Dean. The man you killed today is not the real Cas. It was a criminal with a similar enough name, who was promised parole if he performed this broadcast. I am the real Cas. From this day onwards, I swear to hunt you down, no matter the cost. I'll see you soon." The tv switches to black.

Sam stares at the blank screen, eyes wide. His hand still clenches the pen he wrote the name down on.

Ruby, on the other side of the couch, is howling with laughter. "Oh my god, Sam, he really got you!"

A knock sounds at the door. "Sam, I have to go up to the precinct. You should come." Sam doesn't respond. Another knock echoes through the room. "Sam?"

Sam blinks a few times, and scowls at the door. "Coming, dad." He slams his hand into the off button on the tv remote. He ignores the way Ruby is still sobbing with laughter and yanks on his backpack, preparing to grin and nod in the face of the case detectives laughing in his face.

* * *

"You're... Jessica, right? The pop star?"

"That's right!" Jessica smiles up at him. "I had to meet you, well, because... I know your secret."

Sam lifts an eyebrow. "Oh?"

"You're...." She drops her voice down to below a whisper. "Dean."

"What?" Sam laughs, as if the funniest joke he's ever heard was just told. His eyes blaze. "How could I be...?"

"I have it too. The notebook." Jessica unzips her purse and pulls up a slim black notebook until Sam can barely see the 'ote' and the end of 'notebook'. Sam immediately knows she isn't lying. 

"How do you...?"

"A reaper named Charlie gave it to me." She blinks up at him. "I want to help you. I believe in your mission. I.... I'll help in any way possible."

* * *

"I haven't figured exactly how Dean is doing his killings. Logically, it's entirely impossible. However, Mr. Winchester, if I had to pin a suspect right here and now, I'm pretty sure that Dean is your son."

Sam stares at the man who claims to be 'Cas'. He takes in the man's curved jawline and scraggly black hair and deep blue eyes and wonders, just for a second, 'how is this man a detective?'. They couldn't be much different in age, so it seems implausible that this is Cas. And yet. Sam furrows his eyebrows at the man. "What?"

"Mr. Cas, you must be mistaken… I understand that anyone is a suspect, but my son has been helping here at the precinct the whole time. He's a morally upright citizen. This accusation seems baseless."

"All I'm suggesting is that he lives with me for a while. Twenty-four hour surveillance. If 'Dean' still kills, well, then we can eliminate Sam from the suspect list." Cas smiles gently, but the edge is clear behind his gaze. He intends to trap Sam in his game. Sam won't let it happen.

"But-"

"Dad. It's fine." Sam shrugs and lets out a breath. "I'm not Dean, so I don't have anything to lose. This'll just prove my innocence, right?"

"If there's nothing to prove that you're Dean, then yes. It'll prove your innocence."

"Then I'll do it." Sam smiles at Cas, splaying out his hands. "I don't have to be handcuffed to you, right?"

Cas shifts in his chair. "Well."

* * *

Sam's idea of an ideal Friday night is a couple cans of soda, reruns of Friends, and writing a few names in the death note. It is not, however, sitting in close proximity with the mysterious detective who's been tracking him for months, handcuffed to his other hand. He glances up at the tv. He at least has 'Friends', but it's the last thing on his mind right now. All he can think about is Cas, who is not but a foot away from him. It's infuriating, to Sam, that the man he needs to kill is so close and yet so far away.

Cas, of course, looks unaffected, which may be infuriating Sam even more. What kind of person even is Cas? He doesn't seem like he focuses on anything but his work and his computer. Does he have a life outside of detective work? Does he even dream about anything else? Sam resists the urge to scoff. People like that piss him off.

"So… what do you do all day?"

Cas glances up for a moment, before looking back down at the computer in his lap. He's typing with one hand. "This."

"That's all? Nothing else?" Sam cocks his head. "You don't seem that much older than me. Don't you have any hobbies or interests? A girlfriend?"

Cas shrugs. "Not the type."

Sam's smile falters for a second. What the hell? "You've gotta have something. Boyfriend, then?"

Cas's fingers halt on the keyboard for a short pause before he keeps talking. Bingo. "Who is he?" Sam grins, scooting ever so slightly over towards Cas.

"That's not…. I don't. Have one." Cas's words are stilted, and Sam almost laughs when he notices that his cheeks are tinted just slightly pink. Maybe he is human, after all. He jumps a bit, though, as Cas turns towards him with wide eyes. "You're unusually calm for someone in your situation."

Sam blinks a few times at Cas, before reaching a hand up to rub at his neck. He laughs awkwardly, and says, "Well, honestly, this is kind of scary. I'm mostly trying to diffuse the tension."

"Scary? How so?"

"Well, I don't know you, and you don't know me." Sam huffs out a breath. "And you think I'm a mass murdering criminal."

Cas shrugs. "Have to keep my options open."

Blinking, Sam lets out a slight chuckle. "I guess that's true. Still, doesn't start our relationship off on such a great foot, huh?" 

Cas doesn't respond, so Sam lets his eyes wander around the room. The other man had rented a hotel room just for the twenty four hour surveillance, so everything was as neat as could possibly be. His eyes drift up to the clock. It was almost 9:30. That means Jess should be doing her job by now. 

A month into his work with the death note, Ruby had told him of a special deal reapers had with humans who possessed the notebook. In exchange for half of his remaining life span, he could be granted 'reaper eyes', which allowed him to see a person's full name just by looking at them. It would cut out half the work he put into finding names for the notebook. It seemed an obvious choice at the time. He didn't know how much longer he had to live, so this deal could easily cut him down to a month or a week left of life. He needed to be alive to impose the laws of the new world, so there was no way he could take the deal.

Jess, however, was willing to do anything for Sam. She had expressed as much, that day on the bridge. So he had her make the deal. Now, she could see anyone's name by just looking at a person's face. This was something he could use.

Currently, as he sat on the couch, Jess was writing names in her death note to continue the pattern of killings he had established. He had suspected something like Cas's plan would occur, so he'd set up this plan with Jess in case he couldn't get to the notebook. As soon as he stepped foot in the hotel, he sent Ruby off to tell Jess of the current situation.

He is going to win this game Cas had set up. It was only a matter of time until the other man tripped up. And then, Dean would strike.

* * *

Sam stares up at the ceiling of the hotel, yawning as the glow of Cas's computer once again kept him from sleeping. It seems as if the other man never sleeps. Which, while Sam is no stranger to all-nighters, is annoying when he just wants the day to be over. "Do you ever sleep?"

The hand on the keys hesitates for half a second. "Sometimes."

Sam turns on his side to face Cas. "When it's, how would you say… optimal?"

Cas glances sideways at Sam. "I don't talk like that."

"Oh? Pray tell, Mr. Cas, how do you talk? Do you know what 'lol' means?"

"Why do you want to know?" Cas raises an eyebrow at Sam. "If your innocence is proven, you'll never see me again." 

Sam shifts over in bed to lay on his back again. "I don't know. I guess I'm just curious about you. You're my age, and yet… you're called the best detective in the country. Maybe the world. How'd you do it?"

There's silence for a long moment. Sam assumes Cas is ignoring him once again, until the silence is broken. "I went to an… academy."

Sam glances over at him. "An academy?"

Cas seems to be intentionally not looking at him. "Not an academy, exactly, but there's no better way to describe it. They trained me to be good at… this." Cas shrugs, just slightly. "It's what I was destined for."

Sam hums. "Destiny, huh. If we go by destiny, then I must be destined to be a detective, like my father."

"Do you wish you could do something else?"

"Well…. You can't tell my dad this, but sometimes, I wish I could be something like, I don't know, a lawyer." Sam splays his fingers out towards the ceiling. "Help those in need. It seems as if the average citizen is left to choke these days. I want to help them."

Cas hums back at him. "Noble of you."

Sam laughs. "You could see it like that." He quiets. "Or maybe it's just a want to be needed by someone."

The room descends into silence. Sam knows he's skipped over a boundary or two, maybe four, but he needs Cas to trust him. He wants Cas to trust him. He looks over at the other man, only to meet his eyes. They're a stunning blue when only met with the glowing white light of the computer screen. He resists the urge to lift his hand up to touch the stubble framing the edges of Cas's face. He feels as if electricity is skittering across his fingers and up his arms and settling in his chest. It's a peculiar feeling. He feels as if the tension in the room went up, but he can't place the origin.

In a surprising move, Cas speaks first. "Maybe you and I aren't as different as we think."

* * *

When Sam steps into his bedroom, rubbing the red mark left around his wrist, he immediately feels a chill down his spine. He knows something is off. He glances up out of the corner of his eye, and if he's right (which he often is), there's a pinprick of red coming from the corner of the room. He keeps his eyes forward and makes a beeline for his desk, opening his drawer to pull out his homework from the previous week.

Ruby, of course, has no qualms about greeting him. "Yo, what's up Sam! I see you're not dead." He does not respond. "Sam?"

Her eyes travel up to the camera in the corner of the room. "Oh, you noticed that too? Good thing no one except you can see me, because you'd have a lot more to explain than a few deaths."

As he completes his math problems in silence, his mind drifts to Cas. The camera means he doesn't trust him. It means that Sam isn't entirely absolved of guilt. It means he has to work extra hard to continue his patterns while staying on Cas's good side.

Still, against his instincts, he feels slightly warm at the concept of Cas looking in on him. 

* * *

"Hey, Cas!" Sam calls out in the precinct. "This is my girlfriend, Jess."

Cas turns around in his chair to look at him, raising his eyebrows at the girl at Sam's side. "Girlfriend?"

Jess smiles brightly. "Nice to meet you, Mr. Cas! I've heard all about you!"

Cas glances over at Sam. "Have you now?"

Sam grins sheepishly. "You left an impression on me, what can I say? We just came to say hi to my dad and decided to drop in here. How's the case?"

"That's strictly confidential."

"Ah, yeah, I get it, you can't tell an old suspect anything." Sam winks at Cas. He pretends he doesn't see the gentle tinge of pink it produces. "We'll head out, then."

Jess waves. "It was nice meeting you!"

"You…. too." Cas responds, before turning back around in his chair towards his computer.

Sam and Jess turn around and walk toward the exit of the building. Sam fights to keep the smirk off his face. He's finally on the winning team. He's going to out-beat Cas at his own game.

* * *

It's late when Sam steps into the precinct. 11:00 p.m. to be exact. He had stolen his dad's key when he'd gotten home, tucking it into his back pocket for later. Everything had been set up. It was time for him to win.

His shoes echo against the hallways, like the hands of a clock ticking. It's all Sam can manage to think, as he tucks his shaking hands in his pockets: 'it's time'.

The door creaks loudly when Sam pushes it open. The room is mostly empty, stations and computers abandoned for the safety and warmth of a home life, except for an important exception; Cas sits, knees tucked up to his chest, at the desk in the middle of the room, computer light filling the corners of his face. Sam tilts his head. Cas knows he's here. "It's a little rude to kidnap and kill a guy's girlfriend, don't you know?"

"It's a little rude to kill millions of civilians, don't you know?" Cas parrots back.

Sam laughs, fully and deeply, bending over and clutching his chest. "I didn't know you knew what comedy was, Cas." He quiets down. "Besides, they weren't really civilians."

Cas spins his chair around to face Sam. "So what were they?"

"Cockroaches." Sam spits out. " _Demons_. Manipulating and hurting the innocents out there who are scared to even walk the streets. The system failed us a long time ago. I was just putting everything back in its place."

"So that was your plan? Kill every evildoer, every person who has wronged someone else?"

"Yes. Start a new world, more black and white than our current broken system."

"And I assume you'd be the new God…?"

"Judgement. Give justice to those who need it."

Cas scoffs. "You didn't give justice. You weren't saving victims. You just promoted fear."

"Fear is the better option against cruelty."

Cas chuckles. There's clear judgement in his tone. Then, a pause for a moment, before he says, "You would've made a good lawyer. Very all or nothing."

Sam smirks. "Too bad you won't be here to see me do it."

"How'd you do it? Kill all of these people without ever touching them?" 

"I don't suppose you believe in the supernatural?" Cas raises an eyebrow. Sam laughs. "I didn't either. But this reaper… he gave me a notebook. You write a name and picture a face, and they die."

Cas takes in a breath, his eyes widening. "Genius. No way to track where the death comes from."

"Exactly. It made for the perfect weapon. I never had to load the gun, just aim and shoot." Sam pulls a slip of paper out of his pocket, folded into a neat square. "And it's aimed for your head, Cas. Or should I say, Castiel Novak. Thank Jess and Charlie for that one. Or, well, you killed Jess, huh?"

Cas is silent for a moment. He seems vulnerable in a way that Sam has never seen him. "Were you truly with Jess?"

Sam blinks. "She was in love with me."

"But not you with her?"

Sam shrugs. "Does it matter?"

Cas smiles, lopsided and melancholy. "I guess not. Just wanted to know if I was hallucinating."

The clock at the corner of the room ticks louder and louder. 11:55. Sam shifts his foot and says, in a voice he feels is quieter than the clock, "It's time."

At first, there doesn't seem to be a change. But then, a small droplet of blood trickles out of the side of Cas's mouth. Then two. Then three. Soon after, he falls out of his chair onto the floor, gasping for air. Sam slowly approaches and kneels down near him. He whispers, tone soft, "You were a good adversary. I'm almost glad that, out of anyone to go up against, it was you."

Cas's eyes flash with amusement before they start to fade. His hand weakly grips at Sam's wrist as he gurgles out, "I'll see you on the other side, Sam", before collapsing with finality on the cold, marble floor. 

The silence beyond this moment is defeaning. Sam stands there, quiet and cold, frozen in time. The clock no longer ticks, and the room no longer moves. Even the computer seems to have faded into background noise, inconsequential to this moment. Sam hovers somewhere between ecstatic and devastated. He stares at Cas's corpse and thinks of the night in the hotel and the way Cas looked at him. He thinks of the way he's never told anyone his lawyer dream before. He thinks of Cas's blue eyes. 

Clapping echoes in the corners of the room. He thinks he's imagining it, until a voice booms through the room, "Well, a midnight death. A little cliche, hmm?"

Sam turns around to the face of Ruby, smirking at him. He raises an eyebrow. "What are you doing here?"

"Getting my happy ending, as they say." She shrugs. "Or an ending in general. Never was for human archetypes."

"What do you mean?"

"Well, you didn't think I was just going to let you infinitely use my death note, did you? I had to take it back some time." She lifts her hand and the death note appears in her palm. "The game is over." 

Sam stares as she leafs through the pages of the notebook. "So, that's it? You're cutting me off cold turkey?"

She glances up at him and chuckles. "Cold is one way to put it." A pen appears in her other hand as she scratches something into the notebook before they both disappear.

Sam begins to feel fear crawling up his back. "What did you just do?"

"Ended the game. And you know, you gotta admit, I'm _awesome_. This has been the most interesting game yet. I mean, I finally wasn't bored there for a while. You and Cas had something special." Ruby winks. "There was never really meant to be a winner here."

Black crawls up the sides of Sam's neck. He collapses on the ground, gasping desperately for air. It feels as if his insides are trying to crawl out of him. His vision is going blurry. "W-why…"

Ruby smirks. "There is no God in this world. Only cockroaches to be smashed. Good try, _Dean_."

Pen to paper. The clock stops at exactly 12:05 a.m. Sam and Cas lay together, cold and unchangingly grey, on the precinct floor. The best stories never end with goodbyes.


End file.
